Acoustical panel having openings and ceramic surfacing material bonded to the panel



United States Patent 3 348 996 ACOUSTICAL PANEL HAVING OPENINGS ANDCERAMIC SURFACING MATERIAL BONDED T0 N THE PANEL John E. Cadotte, 2427Western Ave. N.,

St. Paul, Minn. 55110 No Drawing. Filed Apr. 7, 1966, Ser. No. 540,809

, 2 Claims. (Cl. 162-114) This application is a continuation-in-part ofmy copending application Ser. No. 427,545, filed Jan. 25, 1965, as acontinuation-in-part of the now abandoned applications Ser. No. 149,199and Ser. No. 193,299, filed May 8, 1962 as a continuation-in-part ofsaid Ser. No. 149,199, filed 'Nov. 1, 1961. i

The present invention relates to acoustical panels having a poroussound-absorbing body portion free of organic content and consistingessentially of ceramically bonded fiber felt and particulate ceramicmaterial such as clay distributed throughout the felt. The porous bodyportion has a multiplicity of acoustical openings exposed to the receiptof sound and extending into the body portion from one face thereof.

Feigley et al. No. 3,014,835 discloses various combinations of equalparts of mineral fibers and of particulate .er than drilled holes, havebeen widely used as acoustical panels, especially in ceilings. Suchpanels in felted fiber form having mineral fibers, or vegetable fibers,or a mixture of such fibers have been widely used as lay-in panels, forexample, panels 2 ft. by 4 ft. in size, supported by underlying marginalsupport flanges. In such panels the fibers are bonded by adhesive,usually starch. The fibers in the case of vegetable fibers, and theadhesive in the case of starch or like adhesives, are adversely affectedby humid air, and at high humidity, tend to soften and allow the panelto sag.

The present invention modifies porous fired felted mineral fiber panelmaterial, disclosed in and comprehended by my copending application Ser.No. 427,545, and its said predecessors. Therein, panels are formed frommixtures of 100 parts of feltable fiber predominating in mineral fiberand from to 250 parts of particulate material, the mineral fiberconsisting in one type of operation of 75 to 88 parts of syntheticmineral fibers, such as mineral wool, and from 2 to parts of asbestosfiber-s, with from 0 to 10 parts of cellulosic fiber, exemplifying useof 30 parts of kaolin clay to 100 parts of such feltable fiber toproduce a porous dry unfired mat of pounds per cu. ft. The presence ofvegetable fibers in the preform for firing enhances porosity of thefired panel but lessens the strength of fired panels.

For the present invention wherein adequate porosity is desired, theparticulate material is used in amount not greater than the amount ofthe fibrous material. Such panels are characterized by a porousfibrous-network resulting from firing a mineral fiber felt in thepresence of particulate material which in the firing is ceramicallybonded to the network, being originally substantially uniformlydistributed in the unfired mineral fiber felt, referred to as a preformfor firing.

In my said copending application there is described a method ofproducing the preform of the mineral fiber felt Calcium chloride 0 Waterice carrying the particulate material by forming a slurry of the fibersand the particulate material, with or without a binder, preferablystarch, flocculating the slurry and dewatering the suspension of tlocsto form a wet mat. The wet mat has a variable density dependent upon themethod of dewaten'ng, which may or may not include suction through themat. Such density of formation may be increased by pressing. The higherthe density the less porous is the mat when dried, but the strength isgreater for handling the wet or dry mat.

Strength of the dried mat is greater by including a bind- -er in theslurry to bond the contents of the mat upon drying. Starch is thepreferred binder. However, clay as the particulate material has a slightbinding action, but increased content of clay leads to greater densityof formation and this minimizes porosity. Although starch may be used insolution form, starch grains are preferred for convenience. In eitherform the starch is fiocculated so that it is not freely suspended in thewater drained away. As described, a small quantity of a surface activeflocculant is used, such as a polyac-rylamide flocculant, preferablywith a small quantity of a polyvalent metal salt, as illustratedhereinafter.

In firing, the first effect is to burn out or carbonize the organicmaterial. In the case of starch a carbon residue is first formed whichon prolonged exposure can be oxidized, if desired, but its presence inthe resulting small quantity is of no consequence relative to acousticalvalue, and to appearance when surface coating is practiced. Since thefired product has acoutic openings, it is preferred to form them in thedried mat before firing, thus creating bonded. Bonding temperatures upto 2000 F. may be used to retain the described porous skeleton network.Higher temperatures can lead to fusion and thus lessen porosity.- V

In firing such a drilled or punched starch-bonded dry mat, it has beenfound that the porosity and sound-absorbing capacity are increased overthose properties of the dry mat. By firing it, and thus eliminating thestarch, ability to sag with humidity is eliminated.

The invention is illustrated by the examples given below, in which theamount and kind of particulate material and the firing temperature maybe varied.

To a slurry containing parts of mineral fibers, and particulatematerial, with or without binder, is added a solution:

Parts The'slurry is thus converted to flocs suspended in substantiallyclear water, which is quickly drained away by pouring the slurry on ascreen, as is done with a fiber furnish on a 'Fourdrinier machine. Theresulting wet mat is pressed to a suitable density and dried. Whenstarch grains are used, the wet mat is heated in a humid atmosphere to.gelatinize the starch grains, and then dried to bind the contents withthe dried starch. The mat is then either drilled or punched withacoustic holes and fired to bring about ceramic bonding.

The firing temperature can vary over a wide range, but is chosen so as.to avoid fusing the fibers, thus to preserve a skeleton structure. Thisis strengthened by the ceramic bond as the, firing temperatureincreases.

A dry felted-mat without binder formed from 100 parts of mineral wooland 50 parts of Stratton (kaolin) clay,

Polyacrylamide was divided into segments and these were fired attemperatures over a long range, and the modulus of rupture determined.Without binder, the modulus of rupture is very low, large sizesrequiring great care in handling. The

" following table shows how the modulus of rupture is increased byfiring:

Pounds/sq. in.: Temperature, F.

45 800 90 1,200 123 1,400 105 1,600 110 2,000 (Tends to melt) 2,200

Fired panels of the above composition produced at different densitieswere tested for the void space therein, with results as follows:

Density, lbs/cu. ft.: Volume percent, void space The less void space,the poorer is the sound absorption. It has been found that as the kaolinis increased in proportion, the dry mat and the fired panel become moredense with a fixed procedure. Hence, the amount of clay for the presentinvention is not in excess of the amount of fiber,'and preferably ismaintained appreciably below the amount of mineral wool, thus less tofill the voids in the fired skeleton network.

The above table shows that above a density up to 50 lbs/cu. ft., thevoid space of a fired panel begins to decrease. The following examplesillustrate.

EXAMPLE 1 Glass wool is employed.

Parts by Weight Glass wool Kaolin clay 100 Starch grains 1OPolyacrylamide flocculant 0.04 Calcium chloride 1.0 Water 6000 The driedmat Thickness inch 0.882 Density lbs./cu. ft 33 Preform fired at 1420"F. Shrinkage:

Thickness percent 6.4 Area dimensions do- 0.4 Density lbs./cu. ft 32.7Modulus of rupture lbs./sq. in-.. 178

' EXAMPLE 2 Parts by weight White slag wool 100 Kaolin clay 100 Calciumchloride 0.5 Animal glue (dry solids) 5 Polyacrylamide flocculant 0.08water- 3700 I. f The dried mat Thickness inch .575, Density lbs./cu. ft49.7

' Preform fired at 2000" F. Shrinkage: v Thickness v percent 1.8 Densitydo 1.5 Density 1bs./cu. ft 49.7

Modulus of rupture lbs./sq. "in 2482 4 EXAMPLE 3 Parts by weight Whiteslag wool 100 Kaolin clay 50 Ground felspar 50 Tapioca starch grains 10Water 3700 Polyacrylamide flocculant 0.08 Calcium chloride 0.5

The dried mat Density lbs./cu. ft 48 Preform fired at 2000 F Shrinkage:

Thickness percent 0.3 Area dimensions do 0.8 Modulus of rupture lbs./sq.in 167 The low shrinkage indicates substantially no decrease in densityon firing.

In the following Example 4, the dried mat was drilled in a random mannerwith 4-inch and Y -inch diameter drills totaling 319 holes per sq. ft.

The acoustic property of the panel of Example 4, known as d wasdetermined by the standard impedance tube test of American Society ofTesting Materials, designated C384-56T. This is the average of 0:0 forsound at 250, 500, 1,000 and 2,000 cycles per second.

Solid Back 10 Airspace Before firing After firing The board was inchthick before firing.

.The test shows that the generally unacceptable d of the punch unfiredpanel was increased to acceptable values merely by firing.

In order to present an acceptable surface appearance, the fired boardmay have selected ceramic material on its surface ceramically bonded tothe body portion. This may be applied to a fired board, which is againsubjected to a firing temperature to efiect the bond. Preferably, it isapplied to the mat before firing so as to produce, a cerarnically coatedfired board in one firing step.

On the main body portion, in one case, an engobe may be formed byapplying to the surface selected ma terial which in the firing sintersto a non-homogeneous covering coat, rather than to a glassy structure orglaze. Such an engobe may form the entire exposed surface of the board.The engobe or the fired board without the 'engobe may be partly orentirely covered by a slip applied to form a glaze coat. The engobe isselected to provide a color or texture for the exposed portions of it,thus to hide the color or appearance of the underlying fired bodyportion. When glaze is formed in a discontinuous coat, such as inspotted areas, the engobe and EXAMPLE 5.-Engobe base composition Anengobe was produced by the following:

Parts by weight, grams Kaolin clay 166 Slag wool, powdered 334 Water 450Sodium tripolyphosphate 1 Commercial ceramic frit 50 1 Such as Ferro3466 made by Fen-o Corporation of Cleveland, Ohio.

EXAMPLE 6.Glaze composition For application to form a glaze on firing,the following was prepared:

Parts by weight, grams Commercial frit (Ferro 3466) 396 Chromium oxidepigment 4 5% Methocel 80 Water 115 EXAMPLE 7 A dry unfired board formedas above described, and acoustically drilled, made from 100 parts ofmineral wool and 50 parts of kaolin clay, at a density of 40 lbs./cu.ft. is coated with engobe, preferably by spraying the entire surface. Inusing the engobe base composition of Example 5, 5.5 parts if zirconiumoxide pigment is added to 200 parts of said composition to produce awhite engobe coat. This coat is-dried.

Then onto the engobe is applied a glaze composition, specifically thatof Example 6, by spraying at a pressure of 15 to 20 pounds per sq. inch,to form a discontinuous coat in the form of spattered areas for thefinal glaze. This is then dried, and the whole fired at 1850 F. Spottedgreen glaze areas with the white background of the engobe gives adecorative effect on a punched or drilled ceramic acoustical board.

The invention is not limited to the exemplary examples, and numerouscombinations of ingredients and of processing steps and variationsthereof, are contemplated as falling within the scope of the appendedclaims.

I claim:

1. An acoustical panel having a porous sound-absorbing body portionconsisting entirely of inorganic material and essentially of aceramically bonded porous body of a mineral fiber felt and ofparticulate ceramic material, said mineral fiber predominating insynthetic mineral fiber, the particulate ceramic material being presentin quantity not exceedng the quantity of fiber, said body portion havinga density up to pounds per cubic foot and having a multiplicity ofacoustical openings exposed to the receipt of sound and extending from aface of the body portion into but not through the body por- -tion, saidface having a coat of glaze ceramically bonded thereto at areas otherthan said openings, and said openings at their juncture with the surfaceof said face having smooth fired edges.

2. The method comprising forming a multiplicity of acoustical openingsin a porous panel consisting essentially of a felted network of fiberspredominating in synthetic mineral fibers and of particulate ceramicmaterial distributed throughout the network, applying ceramic surfacingmaterial to the surface of the panel at areas between the openings, andthen bringing about a ceramic bond between the mineral fiber network andthe surfacing material and smoothing the surfacing material at the edgesof the openings by firing the panel.

References Cited UNITED STATES PATENTS 2,063,102 12/1936 Jones 106412,915,475 12/1959 Bugosh. 3,014,835 12/1961 Feigley 162-454 3,017,3181/1962 Labino et al. 162-152 3,086,878 4/1963 Lauring. 3,117,403 1/ 1964Jack et al.

HOWARD R. CAINE, Acting Primary Examiner. DONALL H. SYLVESTER, Examiner.

1. AN ACOUSTICAL PANEL HAVING A POROUS SOUND-ABSORBING BODY PORTIONCONSITING ENTIRELY OF INORGANIC MATERIAL AND ESSENTIALY OF A CERAMICALLYBONDED POROUS BODY OF A MINERAL FIBER FELT AND OF PARTICULATE CERAMICMATERIAL, SAID MINERAL FIBER PREDOMINATING IN SYNTHETIC MINERAL FIBER,THE PARTICULATE CERAMIC MATERIAL BEING PRESENT IN QUANTITY NOT EXCEEDINGTHE QUANTITY OF FIBER, SAID BODY PORTION HAVING A DENSITY UP TO 50POUNDS PER CUBIC FOOT AND HVING A MULTIPLICITY OF ACOUSTICAL OPENINGSEXPOSED TO THE RECEIPT OF SOUND AND EXTENDING FROM A FACE OF THE BODYPORTION INTO BUT NOT THROUGH THE BODY PORTION, SAID FACE HAVING A COATOF GLAZE CERAMICALLY BONDED THERETO AT AREAS OTHER THAN SAID OPENINGS,AND SAID OPENINGS AT THEIR UNCTURE WITH THE SURFACE OF SAID FACE HAVINGSMOOTH FIRED EDGES.